For decoding an MPEG encoded video bitstream in order to navigate through the picture material the information about the encoded GOP structure is necessary. When the encoded GOP structure is known it is possible e.g. to decode and display the video sequence reverse when decoding a Digital Versatile Disc (DVD). The GOP structure is available implicitly but not explicitly in the encoded bitstream and therefor must be extracted. By providing a GOP structure analysis generated during normal decoding, however, a decoding control unit gets all information necessary to control a backward or any other free navigation for trick mode decoding.
To get the implicit GOP structure information explicitly it is known to pre-parse the video bitstream for extracting the GOP structure information and store the information in a memory. In order to get the GOP structure information explicitly a separate parsing software process is needed or dedicated parsing hardware device. The software process needs extra processing power and the hardware device needs extra chip area.